1. Field of the Invention
This invention relates to a variable flow solenoid for the pilot control of an hydraulic valve.
2. Description of Related Art
In hydraulic control systems, it may be required to vary the flow of oil controlling the speed of a mechanical element, for example the speed of a hydraulic elevator. This can be done by employing known solenoid type proportional valves which respond to the signals given by a computer, this having received measurements of the actual speed of the elevator, comparing this speed with the value of a pre-determined target speed and calculating the required adjustment of electrical power to the proportional valve solenoid effecting oil flow to achieve the required correction of elevator speed.
Proportional valves are more complex in their design than standard open-closed type solenoid valves and far more expensive. Both of these types are shown in the drawings (see description of FIG. 1 and FIG. 2 in Brief Description of the Drawings).